JPH0640040B2 - Load detection mechanism - Google Patents

Description

The present invention relates to a load detection mechanism for detecting loads (forces and moments) acting on various objects.

[Conventional technology]

The load detector is used by being attached to various machines and devices, but the operating mode in which the load acts directly on the load detector (the usage pattern in which there is the point of action of the load on the load detector) Rather, the load detector is usually connected to a predetermined portion of a machine, a device, or the like, and the load is usually applied to a certain point of the predetermined portion. Such a configuration will be described with reference to the drawings. In addition, in the following description, the predetermined portion is referred to as a loading portion in the sense of a portion on which a load acts.

FIG. 3 is a side view of a conventional load detecting mechanism. Reference numeral 1 is a rod-shaped loading portion, 2 is a load detecting portion, and 3 is a connecting portion that connects the loading portion 1 and the load detecting portion 2. The load detector 2 includes a case 2a, rigid members 2b and 2b 'connected to the case 2a and the connecting portion 3, and the rigid members 2b and 2b, respectively.
It is composed of the strain-flexing parts 2c and 2c 'installed between 2b', and the load is detected by the strain of the strain-flexing parts 2c and 2c 'generated according to the load transmitted through the connecting part 3. That is, when a force F in the direction of the arrow is applied to one point P of the loading unit 1 and the distance between the point P and the center of the load detector 1 is l, the force F is applied to the load detector 1. A moment (1 × F) acts. Due to these loads, the strain-flexing parts 2c and 2c 'are distorted and the loads can be detected.

In the above load detecting mechanism, the relationship between the force F and the moment M resulting therefrom is M = 1 · F as described above. Therefore, as the rating of the load detector 2, the rated value of force is F
₀ and the rated value of the moment is M _0, both rated values F ₀ ,
It is ideal that the relationship between the M ₀ is set to be in the relationship of _{M 0 = l · F 0 ........................} (1). However, it is impossible to set both rated values F ₀ and M ₀ in the relationship of the equation (1).

That is, assuming that the distance between the two strain-generating parts 2c and 2c 'of the load detector 2 is d, when a force F as shown in FIG. 3 is applied, the force F'acting on one strain-generating part is From the equation of moment balance F ′ · d / 2 = l · F / 2 ………… (2), F ′ = l · F / d ……………… (3) It was but connexion, the force F is the rated value F _0, in fact the strain generating portion 2c of the load detection device 2, rated value F ₀ is the 2c '
Since a force of 1 / d times (l> d) of
It is impossible to set the rated value F ₀ that satisfies the expression (1).

Under the present circumstances, when the load detection mechanism has the configuration shown in FIG. 3, the rating of the load detector 2 is such that the moment that the load detector 2 can withstand when the moment actually acts, It is set as the rated value M ₀ of the moment of 2.

However, if such a setting is made, the range of the force actually used becomes a value much smaller than the rated value F _{0 of the} force determined when the rated value M _{0 of the} moment is set as described above. For detection, the load detector 2 will be used in a low output region in the force detection capability range,
There is a problem that accuracy and resolution are deteriorated. Such a problem similarly occurs when the loading portion is vertical instead of horizontal as shown in FIG. The following explanation
This is because l is too large compared to the size of the load detector 2, and the above description is valid regardless of the structure of the load detector 2.

FIGS. 4A and 4B are a plan view and a side view of a conventional force detection mechanism. In the figure, 1A is a disk-shaped loading portion, 2A,
Reference numerals 2B and 2C are force detectors, and 3A, 3B and 3C are connecting portions that connect the force detectors 2A, 2B and 2C to the loading portion 1A. X, Y, and Z indicate coordinate axes. Each force detector 2A, 2
B and 2C are so-called triaxial force detectors that detect force components in the directions along the coordinate axes X, Y, and Z, and are arranged in the illustrated positional relationship at the edge of the loading portion 1A. In such a configuration, when a force acts on the loading section 1A, the force and the moment due to this force are shared by the respective force detectors 2A, 2B, 2C, so that at any point on the loading section 1A It is obvious that a large force close to the rated value of can be applied.

Here, the detection principle of this force detection mechanism will be described with reference to FIG. Now, in the X-Z axis plane, the force F is fifth at the point P on the straight line connecting the connecting points A and B of the force detectors 2A and 2B.
Consider a case in which it acts in the direction shown in the figure.

l: Distance between points A and B a: Distance between points A and P t: Thickness of loading section 1A F _XA , F _ZA : Forces in the X-axis and Z-axis directions received by the force detector 2A F _XB , F _ZB: force detector 2B receives X-axis and Z-axis direction force M _a, M _B: force detector 2A, when the moment 2B receives, in the X-axis direction force F force components F _X and Z-axis direction The force component F _Z is F _X = F _XA + F _ZB ……………… (4) F _Z = F _ZA + F _ZB ……………… (5) and the moment balance _{more, tF X + aF Z = -M} A -M B + lF ZB ...... (6) holds. F _XA , F _XB , F _ZA , and F _ZB are force detectors 2A,
Since the detected value is 2B, the magnitude and direction of the force F can be detected from the expressions (4) and (5).

[Problems to be solved by the invention]

By the way, to obtain the position a of the force application point P of the force F (6)
It is necessary to know the values of the moments M _A and M _B from the equation, but these values are unknown. Therefore, when this mechanism is used, the calculation of the equation (6) is executed with M _A = 0 and M _B = 0 for the convenience of obtaining the position a. In some cases, there is no problem even if the position a is obtained by performing such calculation, but the force detectors 2A, 2B, 2C and the loading unit 1A are
Since a flexure occurs when a force or moment is applied, even if the equations (6) are calculated with the moments M _A and M _{B set} to 0, the accurate position a cannot be obtained, and the detected value of the position a is highly accurate. In the mechanical device that requires the above, there is a problem that the above force detection mechanism cannot be used.

The object of the present invention is to provide a load detection mechanism capable of not only applying a force close to the rated value in a wide range but also accurately detecting the position of the action point of the force, excluding the above-mentioned drawbacks of the prior art. To provide.

[Means for solving problems]

In order to achieve the above object, the present invention uses a detector capable of detecting both a force and a moment as a load detector, and connects a plurality of the load detectors to one loading portion at intervals. Characterize.

[Action]

A load detector capable of detecting both force and moment is connected to one loading section. In this case, the rated values of force and moment can be properly set by adjusting the distance between the load detectors to an appropriate distance.

〔Example〕

 Hereinafter, the present invention will be described based on the illustrated embodiments.

1 (a) and 1 (b) are respectively a plan view and a side view of a load detection mechanism according to an embodiment of the present invention. Reference numeral 5 is a disk-shaped loading portion, and 6A, 6B and 6C are load detectors equivalent to those shown in FIG. Reference numerals 7A, 7B and 7C are connecting portions that connect the load detectors 6A, 6B and 6C to the loading portion 5. Each load detector 6A, 6B, 6C is a loading unit 5 respectively.
Are arranged at substantially the same distance from each other.

In such a configuration, when a force acts on a certain portion of the loading portion 5, the moment generated by this force depends on the magnitude of the force, the direction, and the distance from the point of action of the force on each load detector 6A, 6B and 6C share the load detector, and a smaller moment acts on each load detector. In other words, even if the rated values of the moment of the load detectors 6A, 6B, 6C are the same as the rated values of the moment of the conventional load detector 2, the rated value of the moment of the entire load detecting mechanism is selected to be large. Therefore, the magnitude of the force that can be applied can be increased. Therefore, when viewed from the load detectors 6A, 6B, and 6C, a larger force component can be applied to a certain predetermined axis, and the force can be detected in a wider range within its rated value. . In order to further exert such an effect, the distance between the load detectors 6A, 6B, 6C may be adjusted to an appropriate value depending on the magnitude of the force and the moment.

Here, a means for obtaining the force F and its point of action in this embodiment will be described. Now set the coordinate axes as shown,
Also, G: on loading unit 5, a line l ₁ connecting the load detector 6A, the center of 6B: load detector 6A, the distance between 6B l _2: the vertical distance between the load detector 6C and line G P: Power F acting point a: Distance in the X-axis direction between the load detector 6A and the acting point P b: Vertical distance between the acting point P and the line G t: Thickness of the loading portion 5 F _XA , F _YA , F _ZA : Load Force components in each axial direction detected by the detector 6A M _XA , M _YA , M _ZA : Moment components around each axis detected by the load detector 6A F _XB , F _YB , F _ZB : In the load detector 6B Force components in each axial direction detected M _XB , M _YB , M _ZB : Moment components around each axis detected by the load detector 6B F _XC , F _YC , F _ZC : Each detected by the load detector 6C axial force component _{M XC, M YC, M ZC} : When the moment component about the respective axes detected by the load detector 6C Each axial component F _X of the force F, F _Y, F _Z is expressed by the following equation.

F _X = F _XA + F _XB + F _XC ………… (7) F _Y = F _YA + F _YB + F _YC ………… (8) F _Z = F _ZA + F _ZB + F _ZC …………… (9) Furthermore, from the balance of force and moment, The components F _X , F _Y , of the force F obtained by the equations (7), (8), and (9)
The magnitude and direction of the force F can be determined from F _Z. Further, the distances a and b can be obtained by the equations (7) to (9), and the action point of the force F can be obtained.

Next, when an arbitrary moment is applied to a certain location of the loading section 5, the components of the moment around each axis are M _X , M _Y , M
_{When Z} is set, the following equations hold.

The moment can be accurately obtained from the moment components M _X , M _Y , and M _Z obtained by the equations (16), (17), and (18).

FIG. 2 is a side view of a load detecting mechanism according to another embodiment of the present invention. In the figure, the same parts as those shown in FIGS. 1 (a) and 1 (b) are designated by the same reference numerals and the description thereof will be omitted. In the figure,
Reference numeral 5'denotes a rod-shaped loading portion fixed to an appropriate portion of the loading portion 5. The present embodiment differs from the previous embodiment only in that the rod-shaped loading portion 5'is provided.

As such a load detecting mechanism, for example, a case of a robot hand of the rod-shaped loading portion 5'is assumed. In this case, since the configuration of the previous embodiment is used,
This load detection mechanism can withstand a large force even if a large force is applied to the tip of the rod-shaped loading portion 5 '(robot hand) and a large moment is generated, and force detection should be performed in a well-balanced manner. You can Further, as described in the previous embodiment, since the point of action of force can be detected, it is possible to accurately perform fitting work by a hand or cutting work performed by attaching a grindstone to the tip of the hand. it can.

In the description of each of the above-described embodiments, an example in which three load detectors are used has been described, but the present invention is not limited to this, and it is clear that the number may be two or four or more.

〔The invention's effect〕

As described above, in the present invention, the load detectors capable of detecting the force and the moment are connected to one loading portion at intervals, so that the force rating of the load detector is large in the configuration in which a large moment acts. Not only the force close to the rated value can be applied in a wide range with respect to the value, but also the position of the action point of the force can be accurately detected.

[Brief description of drawings]

1A and 1B are a plan view and a side view of a load detecting mechanism according to an embodiment of the present invention, and FIG. 2 is a side view of a load detecting mechanism according to another embodiment of the present invention. FIG. 4 is a side view of a conventional load detection mechanism, FIGS. 4 (a) and 4 (b) are plan views and side views of a conventional force detection mechanism, and FIG. 5 is FIG. 4 (a),
It is an action principle figure of the mechanism shown in (b). 5 ... Loading part, 5 '... Rod loading part, 6A, 6B, 6C
…… Load detector.

Claims (2)

[Claims] 1. A loading section on which a force acts, and a plurality of detectors connected to the loading section with a space therebetween and detecting a force component in a predetermined axial direction and a moment component about a predetermined axis. A load detection mechanism characterized by being configured. 2. The detector according to claim (1), wherein the three detectors are connected to the load section at substantially equal intervals from each other, and each detector has three orthogonal axes. A load detecting mechanism having a configuration for detecting a force component acting in a direction along the axis and a moment component acting around the three axes.